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We undertook to discuss the question whether sight is possible
in the absence of any intervening medium, such as air or some
other form of what is known as transparent body: this is the time
and place.
It has been explained that seeing and all sense-perception can
occur only through the medium of some bodily substance, since in
the absence of body the soul is utterly absorbed in the
Intellectual Sphere. Sense-perception being the gripping not of
the Intellectual but of the sensible alone, the soul, if it is to
form any relationship of knowledge, or of impression, with
objects of sense, must be brought in some kind of contact with
them by means of whatever may bridge the gap.
The knowledge, then, is realized by means of bodily organs:
through these, which [in the embodied soul] are almost of one
growth with it, being at least its continuations, it comes into
something like unity with the alien, since this mutual approach
brings about a certain degree of identity [which is the basis of
knowledge].
Admitting, then, that some contact with an object is necessary
for knowing it, the question of a medium falls to the ground in
the case of things identified by any form of touch; but in the
case of sight- we leave hearing over for the present- we are
still in doubt; is there need of some bodily substance between
the eye and the illumined object?
No: such an intervening material may be a favouring circumstance,
but essentially it adds nothing to seeing power. ! Dense bodies,
such as clay, actually prevent sight; the less material the
intervening substance is, the more clearly we see; the
intervening substance, then, is a hindrance, or, if not that, at
least not a help.
It will be objected that vision implies that whatever intervenes
between seen and seer must first [and progressively] experience
the object and be, as it were, shaped to it; we will be reminded
that [vision is not a direct and single relation between agent
and object, but is the perception of something radiated since]
anyone facing to the object from the side opposite to ourselves
sees it equally; we will be asked to deduce that if all the space
intervening between seen and seer did not carry the impression of
the object we could not receive it.
But all the need is met when the impression reaches that which is
adapted to receive it; there is no need for the intervening space
to be impressed. If it is, the impression will be of quite
another order: the rod between the fisher's hand and the torpedo
fish is not affected in the same way as the hand that feels the
shock. And yet there too, if rod and line did not intervene, the
hand would not be affected- though even that may be questioned,
since after all the fisherman, we are told, is numbed if the
torpedo merely lies in his net.
The whole matter seems to bring us back to that sympathy of which
we have treated. If a certain thing is of a nature to be
sympathetically affected by another in virtue of some similitude
between them, then anything intervening, not sharing in that
similitude, will not be affected, or at least not similarly. If
this be so, anything naturally disposed to be affected will take
the impression more vividly in the absence of intervening
substance, even of some substance capable, itself, of being
affected.
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